Australia's biggest bank has also made a further $200 million provision for the "currently known" costs it will incur this year for regulatory matters, including the upcoming banking royal commission, and outgoing chief executive Ian Narev acknowledged that there could be more to come.

"We haven't sat down and taken a provision for absolutely every outcome we think might be likely - what we have talked about is some of the things that we think are those most likely."

CBA made the $375 million provision for penalties that could result from the Federal Court case over AUSTRAC's allegations of money-laundering and terrorism-funding law breaches.

With the bank incurring $575 million in total provisions, Mr Narev took a concilliatory tone as he presided over his final set of results as CEO before Matt Comyn takes his place in April.

"We recognise, and regret, that these costs arise from our failure to meet some standards that we should have," Mr Narev said in a statement.

Citi analysts said the underlying performance was strong and that the bank was trying to draw a line under the impact of the AUSTRAC proceedings, but said there was still a risk the final cost would be higher.

Analysts previously estimated costs in the region of $1 billion.

CBA shares closed down 0.8 per cent at $76.79 - the heaviest fall of the big four banks, which all ended in negative territory as the broader market rose on Wednesday.

Pro-forma underlying cash profit excluding the $375 million provision rose 5.8 per cent to $5.11 billion and the bank lifted its interim dividend one cent to $2.00, below analyst consensus of $2.06.

Statutory profit for the six months to December 31 was flat at $4.906 billion, while cash profit, including income from the life insurance business that CBA has agreed to sell to AIA for $3.8 billion, dropped 0.7 per cent to $4.871 billion.

Net interest margin rose 0.06 percentage points over the half year to 2.16 per cent, helped by mortgage repricing to help sway borrowers away from interest-only loans.

Owner-occupier lending grew 7.5 per cent in the 12 months to December 31, while investor lending inched up just 0.5 per cent in the same period as APRA limits on riskier loans continued to take effect.

CBA also trimmed its exposure to apartment development amid widespread concern of oversupply to $4.06 billion, down from $4.51 billion in the prior half and from $5.24 billion a year earlier.

Mr Narev said CBA remained positive about Australia's economic prospects but warned about continued market volatility that could affect the country - and the bank under his successor, Mr Comyn.

"Market volatility remains a risk given ongoing global uncertainty as to the pace and extent of rate rises," Mr Narev said.